Think of electricity like water flowing through a pipe, but instead, it's the flow of energy through wires.  Some of the terms you might hear:

In your home, most outlets (electricians call them receptacles) provide 120 volts, and larger appliances like dryers or ovens use 240 volts. The amperage rating on your electrical panel (such as 100 or 200 amps) tells you how much total electrical current your home can handle at once.

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Electricity reaches your house from your utility company through either overhead wires (known as a service drop) or underground wires (called a service lateral). For a typical house, there are three wires: two hot wires, each carrying 120 volts, and one neutral wire. You’ll likely find a meter on the outside of the house where the electricity enters. Either at the meter or nearby on the inside, you'll find the main electrical service panel, which serves as the distribution center for electricity throughout the house. There may be one or more subpanels off of the main panel, but the main panel acts as the primary distribution hub.

The two hot wires (120V each) enter the main panel and pass through a main breaker (this shuts off power to the entire house). After the main breaker, they then split to supply current to one of two “bus bars” that transfer the current to circuits (see below). Each bus bar is 120V. Circuits that require 120V (most household circuits) use a single circuit breaker on one bus bar. For appliances needing 240V (e.g., central AC, electric oven, electric dryer), a double-pole breaker is used. This double circuit breaker draws current from both bus bars to produce the 240V. 

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While the electricity coming into the house is a standard 240 volts, the main service panel’s amperage rating determines how much total electricity the home can safely use at one time. It affects the home’s ability to power multiple appliances and devices simultaneously. Most modern homes are equipped with 100-amp, 150-amp, or 200-amp panels, though older homes may still have 60-amp panels. A higher amperage panel does not increase the voltage of the home’s electrical supply (which remains 240V), but it does allow more power-hungry appliances to operate simultaneously without overloading the system.

A 100-amp panel can support basic household needs, including lighting, outlets, and standard appliances. However, homes with central air conditioning, electric heating, or multiple high-demand appliances often require a 150- or 200-amp panel to prevent overloading.

If a panel is undersized for a home’s electrical demands, circuit breakers may trip frequently, and the wiring could overheat, creating a fire hazard. Frequent tripping of breakers is something for an electrician to address. Electrical service can be upgraded with a higher-amp panel.

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Electricity flows from the main service panel throughout your house via wires that form a closed-loop system called circuits. The wires are insulated* copper or aluminum that carry electricity from the service panel to outlets (electricians call them receptacles), switches, or appliances, and then back to the panel. Different thicknesses of wire (measured in gauge), are used for different amp circuits. The thicker the wire, the more amps the circuit can carry. 

Circuits can be branch circuits (supplying electricity to multiple lights and outlets) or dedicated circuits (supplying electricity to one item like an air conditioner or oven). There are numerous circuits within a house. For a typical 120V circuit, three wires travel together from the service panel to the outlets, lights, or appliances: 1) a hot wire, 2) a neutral wire, and 3) a ground wire. The hot wire and the neutral wire form the loop for the circuit. 

Without getting technical about alternating current (AC), the outgoing side of a circuit is the hot wire, which delivers current. The return side is the neutral wire, which completes the circuit by carrying current back to the electrical panel. When you plug something into an outlet, or you turn on a switch or appliance, electricity that's already present in the circuit becomes available for the device. Flipping a switch or plugging in a device closes the loop, and more electricity flows through the circuit, powers the device, and returns via the neutral wire back to the panel to complete the loop. As mentioned above, a circuit may supply electricity to a single appliance or multiple outlets and lights.  

*Insulated wire means it's covered with a non-conductive material, typically plastic, to prevent electrical current from flowing outside of the wire.

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Outlets (receptacles) and switches are where you interact with the electrical system. 

There’s not much to say here about switches, except that there are single ones and three-way ones (okay, there are a few other types). A single switch is one switch controlling a light or outlet. It usually has “on” and “off” marked on the switch. A three-way switch uses two switches to control one light or outlet. Usually, the two switches are on opposite sides of a room or at the top and bottom of stairs. These don’t have any “on” or “off” markings on the switch.

A. 120V
Most household outlets are 120V 15-amp outlets, meaning they can deliver 15 amps of current. Older outlets may only have two slots and no half circle (the grounding prong on a 3-prong plug). There are adapters (aka “cheater plugs”) for these, but they need to be used correctly. There’s usually a metal tab or wire with a metal tab that needs to be connected under the screw of the outlet faceplate. But even then, if there’s no ground wire to the outlet, it won’t be grounded. All it does is allow you to plug a three-prong plug into a two-prong outlet. Not the safest thing to do, because it doesn’t protect you from an electrical shock (see Ground Wire below).

There are a few other types of electrical outlets, including:

20-amp receptacles are sometimes used for medium-sized appliances like a microwave oven or refrigerator. You can plug anything into a 20-amp outlet, but you can’t plug a 20-amp device into a 15-amp outlet.

240V receptacles are for equipment that needs more power. These are typically dedicated circuits, meaning they only serve one receptacle, appliance, or piece of equipment. Things like air conditioners, heat pumps, and electric clothes dryers require 240V. There are several different configurations of the slots on the outlet, and it can have three or four slots. The plug configuration on the appliance must match the configuration on the outlet. 

Note: On 120V outlets installed with the ground at the bottom, the larger slot on the left is the neutral, and the smaller slot on the right is the hot. Sometimes, electricians will install an outlet upside down, or with the ground on top of the two slots (called “ground-up”). You'll find differing opinions about why or when to install "ground-up" or "ground-down."

Second note: Sometimes outlets (or one of the two plug-ins on an outlet) are controlled by a wall switch. If you have an outlet that’s not working (or just the bottom plug-in isn’t working), it might be controlled by a switch. 

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Circuit amperage refers to the amount of electrical current a circuit can safely handle. It’s measured in amps and is determined by the breaker size at the panel and the wire gauge (thickness) that carries the current throughout the circuit. Most household circuits are 15- or 20-amp circuits, whereas larger appliances like ovens and dryers require 30, 40, or even more amps.

Circuit breakers in the panel limit the amount of current that can flow through a circuit.  When too many devices draw power from a circuit and exceed its amperage rating, the breaker trips. The circuit breaker will open the loop (breaking the circuit) to stop the flow of electricity, preventing the wiring from overheating and potentially causing a fire. When you have a tripped breaker, you can reset it at the service panel.

In an older home’s electrical system (if the system has not been upgraded), fuses serve as safety devices designed to protect circuits from overloading. Each fuse has a thin metal wire that melts when too much current flows through it. If a circuit becomes overloaded or experiences a short, the excessive current causes the wire to heat up and break, halting the flow of electricity. This action prevents overheating, reduces the risk of electrical fires, and safeguards appliances and wiring. After a fuse blows, it must be replaced with a new one of the same amperage to restore power.

Along with the hot wire that carries the current through a circuit and the neutral wire that carries the current back to the panel, there's also a ground wire. This is typically a bare copper wire (no plastic insulation on the wire). A ground wire protects a house’s electrical system by providing a safe path for excess electricity to travel to the earth (ground), preventing shocks and fire hazards. 

If a fault occurs (like a damaged wire or short circuit), anything metal that’s touching the circuit could become electrified. When a person touches the electrified metal, the electricity would travel through them to the ground, shocking the person. A ground wire directs any stray electricity away from appliances and people, instead sending it back to the electrical panel and triggering the breaker to shut off power. This helps prevent electrical shocks, equipment damage, and overheating in the system.

Older houses, pre-1960s or 1970s depending on the area, might not have a ground wire. If your home has two-pronged outlets, they are likely ungrounded. Additionally, if you own an older home with three-prong outlets, they may not be grounded either; these outlets may have been added for convenience to accommodate three-prong plugs. You can verify if the three-prong outlets are grounded and wired correctly using an inexpensive three-prong outlet tester.

GFCI (ground fault circuit interrupter) and AFCI (arc fault circuit interrupter) are safety devices installed as an outlet or as a circuit breaker. In general terms, GFCIs protect against an electrical shock, and AFCIs protect against an electrical fire.

With either GFCI or AFCIs, when installed as an outlet, it's usually the first outlet on that circuit, because (when wired correctly) all downstream outlets on the circuit are also protected, even though they don't look like GFCI outlets (there's no button to push). But it depends on the situation. Sometimes you'll find additional GFCI outlets downstream, for example, if there's an appliance you don't want to have turned off if an upstream outlet is tripped. 

In pseudo-technical terms, GFCIs work by constantly monitoring the electrical current flowing through a circuit. The current (measured in amps) should be the same in the hot wire (from the panel to the device) and the neutral wire (from the device to the panel). If the GFCI outlet or breaker detects a difference between the two, even if it's as small as a few milliamps, it instantly cuts off the power to prevent electrical shock. If there is a difference between these two amounts, it’s assumed that the electricity is leaking out - possibly through a person or water. 

An electrical arc is a discharge of electricity that occurs when an electrical current jumps across a gap between two conductive surfaces. It’s an intense spark. This can happen when an electrical wire carrying current is broken or damaged, has a loose connection, or the insulation is missing (mice and other rodents love to chew on the plastic insulation around wires). These arcs create irregular, high-frequency electrical patterns that generate intense heat and can ignite nearby materials. An AFCI outlet or breaker continuously monitors the electrical current and distinguishes between harmless arcs (e.g., from switches or motors) and hazardous ones. If a dangerous arc is detected, the AFCI quickly shuts off power to prevent overheating and fire.